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International Journal for Modern Trends in Science and Technology, 6(10): 103-108, 2020 Copyright © 2020 International Journal for Modern Trends in Science and Technology ISSN: 2455-3778 online DOI: https://doi.org/10.46501/IJMTST061018 Available online at: http://www.ijmtst.com/vol6issue10.html

IMF: To Enhance the Shelf-Life of

Srijeeta Saha

Department of Food Technology, Guru Nanak Institute of Technology

To Cite this Article Srijeeta Saha, “IMF: To Enhance the Shelf-Life of Food”, International Journal for Modern Trends in Science and Technology, 6(10): 103-108, 2020.

Article Info Received on 30-September-2020, Revised on 12-October-2020, Accepted on 15-October-2020, Published on 21-October-2020.

ABSTRACT

Drying is the oldest method of . By reducing the moisture content and water activity the microbial stability of the food materials can be increased. The minimum water activity (aw) for microbial growth is approximately 0.6. But in case of dehydration the texture, palatability and some physical properties of the food materials can be decreased. Intermediate moisture food (IMF) are shelf-stable products having water activities of 0.6-0.84, and the range of the moisture content from 15%-40% and are edible without rehydration. Osmotic dehydration has many advantages include low processing temperatures, short drying times, and 20%-30% lower energy consumption than typical dehydration processes. is the most important agent used as the humectants for candied intermediate moisture fruits, and salt is used for intermediate moisture vegetables and fish. Most of the fresh fruits can be transformed into IMF or candied fruit (also known as crystallized fruit) without adding synthetic colors and flavors or gelling agent. In this review paper the how different IMF enhance the self-life of the food materials are discussed.

KEYWORDS: Intermediate moisture food (IMF), Osmotic Dehydration, Shelf-life, water activity.

INTRODUCTION highest efficacy, about 10-15 times better than Intermediate moisture are shelf stable BHA[2] which is a radical scavenger. IMF is based products.[1] The purpose of IMF is to achieve a on a cereal: legume mixture with calcium and water activity(aw) that the food can be stored safely flavour, which supplies proteins, carbohydrates without refrigeration but the quality of food will be and vegetable oils; high energy density (3.22 cal/g) totally fine by using sugar syrup or many types of and covers up to 51% of calcium needed. [3] It can sweetening agent. The mixing of ingredients to be easily consumed as a tasty and soft food. This achieve a given (aw), which is allowed safe storage types of foods have a water activity (aw) of 0.80, for to maintain enough water for palatability on an it can be stored at room conditions. empirical basis. Intermediate moisture foods (IMF) Methylcellulose, , citric acid, are rely heavily on the addition of humectants and modified starches are the agents for making preservatives to prevent or reduce the growth of intermediate moisture foods.[4] . The rates of chemical reactions deteriorate foods prepared to an intermediate SHELF-LIFE & SAFETY moisture content and water activity (aw). The water The main purpose of IMF is to achieve a water [2] content is the controlling factor for lipid oxidation activity (aw) that the food can be stored safely model systems comprised of a solid support and an without refrigeration. The shelf life of a food is the oxidizable liquid. Metal chelating agents like EDTA time during which a food retains an acceptable give good protection to oxidation i.e. exhibited the quality from a safety and organoleptic view that

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depends on four main factors: FORMULATION, PROCESSING, PACKAGING AND STORAGE CONDITIONS.[5] A named Staphylococcus aureus which concerns as it can grow and produce specific enterotoxins in water activities of 0.83-0.86 under aerobic conditions. For this reason, proper handling, storage, hygiene and good manufacturing practices are necessary to prevent Staphylococcus aureus. The of P.G. = propylene glycol. Aspergillis and Penicillium species can grow and produce harmful mycotoxins at water activity 0.77-0.85.[6]There are some primary pathogens of concern with low moisture foods and IMFs like Salmonella and Bacillus cereus,[7] which causes the most illnesses associated with low moisture foods or IMFs. A combination of a low pH, addition of sugar, salt and preservatives, and any thermal process are used to reduce the risk of bacterial growth that can eliminate pathogens and extend shelf-life. Chemical preservatives such as sorbate Fig.1:Rate of reactions vs water activity graph [9] and propionates are used in case of and molds to inhibit their growth. Here is a bar graph to show the shelf life of different foods.[8][12] [13]

Fig2: moisture content vs water activity graph[10]

Water Activity (aw) [11]:

Analysis of examples of Intermediate moisture The unbound water is termed as the water activity foods:[9] (aw).[12] The ratio of vapor pressure of water in food to the vapor pressure of pure water at the same temperature is defined as water activity. Solutes are dissolved in water to bind the water molecules and to make them not available for microorganisms to use.[13] It is measured on a scale of 0 (no moisture) to 1.0 (pure water). To describe the water

activity (aw) of air, the term “Relative Humidity

(RH)”, which is (awx 100)? By having a water activity below 0.90, most bacteria are not able to grow in foods. Browning, staling and oxidation are the undesired chemical reactions for baked food

products, greatly influenced by aw as well. [14]

Characteristics of some recently developed IMFs [9]

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Fig 5: Water in air vs temperature graph. Fig3: Water activity vs water content graph [15] Process for IMFs:[20][21] There are many processes to have intermediate moisture foods with low water activity. Some ways of processing is described below [22] :  Partial drying[23]:

Partial drying [24] is the most employed for raw foods that naturally have a high amount of humectants such as raisins, apricots, prunes and sultanas to achieve a water activity between 0.6-0.84 in food products. Humectants are basically solutes (such as sugar or salt) which immobilize water in food. The process of drying removes free water, and the Fig4: Water activity vs moisture content graph [16] humectants [25] in the product bind the rest of water not allowing the water to be utilized for Definition of (aw): chemical reactions or for microbial use.[26][27] aw = p/p* Where p is the partial vapor pressure of water in the solution, and p* is the partial vapor pressure of pure water at the same temperature. Alternate definition:[17]

aw = lwxw

Where lwis the activity coefficient of water and xw is the mole fraction of water in the aqueous fraction.[18]

Equilibrium relative humidity (ERH): aw x 100% Estimated -free shelf life in days at 210C:[19] MFSL: 107.91-8.1Aw Fig 5: Moisture content vs Ignition time graph Water activity of some intermediate moisture foods:[2][13]  Osmotic drying using a humectants:[29]

Range Food The process named osmotic dehydration[30] is used 0.85-0.75 Sweet condensed milk, fruit for soaking food in highly concentrated solutions of cake, salted fish, molasses, humectants. Salt and sugar are the most jams , dog food, dried fruits, commonly used humectants for the osmotic icings, soy sauce, dehydration process. For osmotic pressure water diffused from the food to the humectant solution. 0.75-0.65 Dates, figs, nuts, Parmesan Humectants replaced the water, which results in a , dulce de leche lowered water activity for the food product.[41] 0.65-0.60 Honey, chocolate bars, marshmallows, biscuits.

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The results of using osmotic dehydration process, we allows the fruit to be more stable at room get in two way mass transfer in regards to the moisture temperature. There are some examples like lost and the gain of solids, with moisture loss being strawberries, prunes, peaches, apricots and much greater than the addition of solids. There are pineapples. By osmotic dehydration, IMF advanges of osmotic dehydration including low blueberries are prepared. Until the desired processing temperatures, short drying times, and moisture level is reached, they are soaked in sugar 20-30% lower energy consumption than typical for one to two days followed by a freeze drying dehydration processes. Sugar is used for candied process. Intermediate moisture fruits and salt is used for Intermediate moisture vegetables and fish. To  Meat:[40] manipulate the sensory properties of the food product, a mixture of humectants can be formulated additionally. Without refrigeration fermented meats, sausage, By using this osmotic drying process, using a jerky, and corned beef can last many months. In humectants result in a soft texture in the final product. the Middle East and Mediterranean countries,  Dry infusion[31]: pastrima is a beef product that is often eaten raw. Pastrima is a type of Intermediate moisture food The combination of partial dehydration and osmotic that can be stored for several months in humid dehydration using a humectant is called dry infusion. climates. Here salt is used for drying to reduce At first the food product is dehydrated and and then the water activity and increase microbial safety. resultant product is added to a humectant solution to are added additionally for preservation. [41] reach the desired water activity (aw). [32]As it results in a higher quality and more appealing product, this  Pet Food:[42] method is desirable. It is two processing steps combined, so more energy is used for this method. By using this dry infusion[33] process we can make IMFs to Pet foods which are semi-moisted such as Chewy produce safe, palatable food that can be consumed dog treats and soft cat treats are shelf-stable, soft much later than it is produced. and have low moisture content. To achieve lower  Formulated Intermediate moisture foods: water activity, ingredients are added to

[51] Intermediate moisture pet foods such as soy flakes To achieve water activity (aw) in the IMF range, many types of foods are specially formulated. Many food and wheat flour in addition to solutes such as ingredients are mixed with salt and/or sugar, and glycerol, salt and sugar. Extrusion is one of the additives (such as sorbate[34] and propylene most used processing techniques, to attain the [43] glycol) and then they are subjected to processing Intermediate moisture pet foods. Intermediate methods such as cooking, extrusion or dehydration to moisture pet foods leave fewer odors and are less get the reasult in an Intermediate moisture final messy than canned wet pet food. Intermediate product.[45] Confectioneries and pet foods are the moisture pet foods are convenient products. So example of Formulated Intermediate moisture foods. Intermediate moisture pet foods are found to be  Water activity of aqueous solutions of some more palatable to pets than dry pet food products. potential food humectants (220C):[35][36] [45]

 Baked goods and Confectioneries:[46]

Cakes are considered as Intermediate moisture foods because their moisture content is in between 18%-28%, and are having low enough water activity that preserve with safety and quality.[47] There are some examples of baked goods and confectioneries that come under this category are fruit cakes, pie fillings, candies, marshmallows, jams, pizza crust. A candy-like product named Applications of intermediate moisture foods: Tutti-frutti that can be made from a variety of [39]  Fruits and Vegetables : fruits, most commonly papaya. Mainly raw pieces To protect against microbial contamination and of unripe papaya are boiled and layered with reduce water activity, sugar is added to fruit. It sucrose until reaching 68 degrees brix. Then the

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solution is air-dried until a moisture content of 25.7% is reached. [13]

Advantages of Intermediate moisture foods: Intermediate moisture foods utilize hurdle technology by lowering water activity (aw), reducing pH and using preservatives, to achieving microbial stability and safety. IMF processing methods can reduce water activity to 0.60-0.84 and most of the bacteria cannot grow under a water activity of 0.90.[46] IMFs are ready-to-eat and not required refrigeration. To prolong shelf life and delay flavor and color changes, nitrites and sulphites are added to food. Propylene glycol is a water activity reducing agent and acts as a plasticizing agent to give food its desired texture. IMF food processing is less rigorous compared to canning, dehydration and freezing and results in less nutrient loss. IMF processes are occurred at lower temperatures, CONCLUSION: pressures, and there is no water leaching of nutrients. Since IMFs do not require refrigeration IMFs are shelf stable and it retains the activity of [50], IMF production is more energy efficient microorganisms by lowering water activity (aw). By compared to conventional processes including using IMF many fruits and vegetables can be stored canning and freezing [48]. IMFs are common in without refrigeration. These are the advantages of developing countries because the energy required IMFs. There are also some disadvantages like for canning and freezing is costly. IMFs are not diabetes patients can’t take IMFs because of their readily subject to spoilage, even if packages have high sugar content (i.e. humectants). been damaged prior to opening, as with thermo References: stabilized foods, because of low water activity [47] (aw). [1] “Hazard analysis and risk based preventive controls for human food: Draft Guidance for industry”. (PDF) [2] Water activity in foods Disadvantages: [3] Food processing and technology: principles and practice (4th ed.). Kent: Wood head publishing/ Elsevier Science. Some of the IMFs contain high levels of additives [4] World Health Organization, Food and Agriculture (i.e. humectants, nitrites, sulphites etc.) which may Organization of the United Nations (2015). “Code of hygienic practice for low-moisture foods”. Codex cause health concerns and possible legal problems. Alimentarius. The cause of concern is high sugar content because [5] Leistnar, Lothar (2000). “Basic Concepts of food of the high calorific intake. So, the efforts are been preservation by hurdle technology”. International journal made to improve the quality of such foods by on food microbiology. [6] Sagar V.R.; Suresh K.P. (2010). “Recent advances in drying decreasing sugar and salt addition, as well as by and dehydration of fruits and vegetables: a review”. Journal increasing the moisture content and aw, but of food science and technology. without sacrificing the microbial stability and [7] Handling and preservation of fruits and vegetables by safety of products if stored without combined methods for rural areas. [8] Food preservation by moisture control: fundamentals and refrigeration.[49] applications. Fruit products from IMFs have potential in [9] “The storage and preservation of meat: ll moisture control”. markets.[49]Applications of this technology[50] are Lawrie’s meat science. to produce stable products at ambient temperature [10] Lothar., Leistner (2002). Hurdle technologies: combination treatments for food stability, safety and quality. is limited by the high concentration of solutes [11] The technology of food preservation. Desrosier, James N. required to reduce water activities to safe levels. (4thed.). This usually affects the sensory properties of the [12] Nature of cakes. Cauvain, S.P.CAKES. food.[51] [13] Microbiologically safe foods for the 21st century. Heredia, Norma., Wesley, Irene., Garcia, Santos, 1961-, [14] Willey InterScience. Oxford: Willey-Blackwell (2009). [15] Lothar., Leistner (1992). “Food preservation by combined methods”. Food Research International.

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